1. Field of the Invention
The invention generally relates to automatic dishwashers for washing cooking utensils. In one aspect the invention relates to a latching mechanism for a door for the automatic dishwasher. In another aspect, the invention relates to a push/pull latch mechanism in which the opening force is independent of the closing force.
2. Description of the Related Art
Known automatic dishwashers include a hinged door and a latch mechanism that prevents the opening of the door and the operation of the dishwasher unless the door is latched in a closed position. Since most dishwashers use a resilient and compressible seal positioned between the door and the dishwasher housing, which inherently applies an opening force to the door when the door is closed, the latch must be able to hold the door in the closed position against the opening force to prevent the inadvertent opening of the door or the leaking of the seal from lack of compression.
Generally, the latches can be segregated into two main categories: a handle-actuated latch and a push/pull latch. U.S. Pat. No. 4,776,620, discloses a handle-actuated latch mechanism that includes a fixed latch housing is provided on the door of a dishwashing apparatus and cooperates with a strike plate on a cabinet, against which the door seats in a closed position, to latch the door in a closed position. The strike plate, in addition to latching the door, concurrently activates a switch, which is fixedly mounted on the door. The strike plate is deformable and is deflected by the latch housing as the door is being closed. Upon the door closed position being realized, the strike plate reassumes its undeflected state wherein it latches the door and activates the switch. Consequently, the structure will positively prohibit operation of the dishwashing apparatus until the door is latched. In order to open the door, a handle is moved which deflects the strike plate away from the latch housing and the switch, deactivating the switch, and enabling the door to be opened.
The push/pull latching mechanism eliminates the need for a movable handle. A common implementation of a push/pull latch utilizes a spring-biased over-center cam and a rigid strike plate. The over-center cam is pivotal between two positions corresponding to the door latched and the door unlatched positions. In the door closed position, the spring force acting on the over-center cam must be sufficient to maintain the cam in the latched position against the inherent opening force of the door. Conversely, in the door open position, the spring force must be sufficient to maintain the cam in the unlatched position until the door is closed. Inadvertent return of the cam to the latched position will render the door inoperable. Thus, the door closure force and door opening force are interdependent, and must be carefully tuned to provide an adequate closure force without also developing too high an opening force, which is very undesirable to most users. Thus, there is a need for a latching mechanism which provides adequate door closure force without too high an opening force, and which can be inexpensively manufactured and assembled.
In one aspect, the present invention preferably comprises an automatic washer comprising a housing with a rear wall from which extends a peripheral wall that collectively define a wash chamber, with the peripheral wall terminating in an edge that defines an access opening providing access to the wash chamber. A door is pivotally mounted to the housing for movement between a closed position, wherein the door overlies the access opening, and an open position, wherein the door is away from the access opening A strike is mounted to one of the housing and the door and is movable relative thereto. The strike has a cam retainer, and the cam is pivotally mounted to the other of the housing and the door for pivotal movement from a latch position, wherein the cam is received within the cam retainer, and a release position, wherein the cam is released from the cam retainer. The cam is located on the other of the housing and the door so that the cam remains substantially fixed relative to the other of the housing and the door while the strike contacts a cam surface of the cam, causing the strike to follow the cam and move relative to the one of the housing and the door until the cam is received in the cam retainer, which results in the cam moving into the latch position as the door is moved from the open to the closed position, and the cam moving into abutting relationship with the strike causing the pivoting of the cam from the latch position to the release position as the door is moved from the closed position to the open position.
Preferably, the cam is biased toward the latch position by a spring mounted to the cam and the other of the housing and the door. The spring has a predetermined spring force to control the door opening force independent of the door closing force. The strike can be a flexible plate having one end mounted to the one of the housing and the door and another end for abutting the cam. The cam retainer can have several suitable structures and is preferably an opening near the another end of the strike.
In an alternative form, the strike is a reciprocally-mounted U-shaped catch, the interior of which defines the cam retainer opening. In yet another embodiment of this aspect of the invention, the cam surface is an inclined surfaces facing the strike.
A stop can extend from the other of the housing and the door into the pivotal path of the cam at a location that prevents the cam from pivoting beyond the latch position as the cam pivots from the release to the latch position.
The automatic washer can further include a switch and a plunger for actuating the switch, both of which are mounted to the other of the housing and the door. The plunger is moveable between an actuating and non-actuating position and is located on the other of the housing and the door so that the strike contacts the plunger and moves it from the non-actuating to the actuating position as the door is moved from the open to the closed position. The plunger can further comprise a guide for receiving an end of the strike to direct the strike into abutting relationship with the plunger as the door is moved from the open to the closed position.
A latch housing can be provided and is mounted to the other of the housing and the door. The cam is pivotally mounted to the latch housing, the switch is mounted to the latch housing, and the plunger is slidably mounted to the latch housing to form a subassembly.
In another aspect, the present invention comprises a latch for an automatic washer comprising a rear wall from which extends a peripheral wall, which collectively define a wash chamber. The peripheral wall terminates in an edge that defines an access opening providing access to the wash chamber, and a door is pivotally mounted to the housing for movement between a closed position, wherein the door overlies the access opening, and an open position, wherein the door is away from the access opening. The latch comprises a strike adapted to mount to one of the housing and the door and moveable relative thereto and having a cam retainer. A cam is adapted to pivotally mount to the other of the housing and the door for pivotal movement from a latch position, wherein the cam is positioned to be received within the cam retainer, and a release position, wherein the cam is positioned to be released from the cam retainer. The cam remains substantially fixed relative to the strike while the strike contacts a cam surface of the cam causing the strike to follow the cam until the cam is received in the cam retainer as the door is moved from the open to the closed position. The cam is moved into abutting relationship with the strike causing the pivoting of the cam from the latch position to the release position as the door is moved from the closed position to the open position.
In yet another aspect, the present invention comprises an improvement for an automatic washer comprising a housing with a rear wall from which extends a peripheral wall that collectively define a wash chamber. The peripheral wall terminates in an edge that defines an access opening providing access to the wash chamber. A door is pivotally mounted to the housing for movement between a closed position, wherein the door overlies the access opening, and an open position, wherein the door is away from the access opening. A compressible and resilient seal is disposed between the peripheral wall edge and the door to seal the door relative to the housing when the door is in the closed position wherein the seal is compressed when the door is in the closed position and applies an opening force to the door in a direction that urges the door toward the open position. The improvement comprises a push/pull latch for retaining the door in the closed position and being moveable from a latch position, where the door is retained in the closed position against the door opening force, to a release position, where the door is free to move away from the housing toward the open position in response to the application of a latch opening force to the push/pull latch, and the latch opening force is independent of the door closing force.